Gas is typically delivered to a patient by systems that generally include a source, a mouth piece or mask and tubing interconnecting these components. “Gas” as used herein is comprised of compressed air, oxygen, helium and oxygen, a mixture of oxygen and medicine, or any other gas that would typically be used for patient care, etc. The following specification is focused on oxygen or an oxygen/medicine mixture, which will be described in detail below, the use of “oxygen” is thus for example only and does not limit the scope of the contemplated invention. To avoid a patient rebreathing his or her exhalation and, thus not receiving a fresh or sufficient supply of oxygen and/or medicine, gas delivery systems may also include a one-way valve to prevent exhaled air from mixing with the incoming supply of oxygen or aerosol mixture. The pressure generated by the patient's exhalation is sufficient to close the valve such that the exhalation vents through an outlet port. The pressure generated by the patient's inhalation is sufficient to open the valve, allowing the patient to breath in the prescribed oxygen or aerosol mixture.
Typically the oxygen source continuously outputs oxygen at a predetermined but variable rate or pressure. When the patient is not inhaling, oxygen continues to be delivered wherein the excess oxygen is vented to atmosphere through the outlet port and/or through the mouth piece. Medicine may also be delivered to a patient through a similar delivery system. For example, a nebulizer may be added to the oxygen delivery system such that liquid medicine is aerosolized and mixed with the oxygen flow. A nebulizer may also be used with a system that uses ambient air, rather than oxygen, as the carrier for the aerosolized medicine. In either case, the same problem of waste exists. That is, when the patient is not inhaling, the aerosolized medicine continues to be supplied by the oxygen source and the mixture (medicine plus ambient air and/or oxygen) is vented to the atmosphere. To account for the loss of medicine, health care providers typically over prescribe medicine delivered by this method. Generally, a patient's inhalation accounts for approximately one-third of the breathing cycle, with the remaining two-thirds being exhalation and dwell time. Thus, three times the required dosage may be prescribed to accommodate system losses, which is wasteful and increases health care costs.
One attempt to solve the problem of waste has been to add a reservoir bag to the delivery system. The intended purpose of a reservoir bag is to capture the oxygen and/or aerosolized medicine that is delivered during those time periods when a patient is not inhaling, rather than vent it into the atmosphere. When the patient does inhale, it is intended that the oxygen and/or aerosolized medicine stored in the reservoir bag is available to be inhaled, together with the oxygen and/or aerosolized medicine that is being continuously output from the supply source. Accordingly, it is intended that less oxygen and/or aerosolized medicine is wasted and there is an available reserve of oxygen and/or aerosolized medicine in the reservoir bag for the patient to inhale when the inhalation process starts.
Often reservoir bags are constructed of relatively thick walls and material to provide durability to withstand damage in shipping, handling and use. Due to the thick walled construction, the reservoir bag does not inflate well, if at all. More specifically, as the pressure required to inflate a thick walled bag is greater than the pressure required to open the previously-discussed one-way valve, the pressurized oxygen will seek the path of least resistance and will be fed to the mask and ultimately wasted. That is, the one-way valve opens without the reservoir bag being filled and the oxygen and/or medicine is vented to atmosphere through the outlet port rather than filling the reservoir. One ineffective response to this problem is to increase the pressure of the oxygen or aerosol delivery which would ideally inflate the bag. However, if the initial, lower pressure is sufficient to open the one-way valve, increasing the pressure will have the same effect. Even if the reservoir bag opens as a result of the increase in pressure, once the one-way valve is open, the oxygen or aerosol mixture will vent to atmosphere instead of filling the reservoir. Moreover, increasing the pressure of the system results in a greater flow rate of the oxygen and/or aerosolized medicine which means more oxygen and/or aerosolized medicine will be lost through the outlet port than when the system was operating at a lower pressure. Another way to address this drawback is to reduce the size of the opening of the outlet port. Applicant owns U.S. Pat. No. 5,613,489 directed to an outlet port valve with an adjustably sized opening, the entirety of which is incorporated herein by reference. However, even if the outlet port is reduced in size, the one-way valve will inevitably open to allow oxygen or aerosol to escape through the outlet port.
Accordingly, there is a long standing and unresolved need to provide a reservoir system for use with an oxygen or aerosol delivery system whereby a reserve of oxygen or an aerosolized medicine mixture is created in a reservoir when the patient is not inhaling, thereby eliminating or substantially reducing the waste of medicine and/or oxygen and ensuring the patient receives the prescribed dosage of each—without harming the patient.